Infectious Diseases Flashcards
Infections
A disease caused by microorganisms, especially those that release toxins or invade body tissues
Colonization
Harmless inhabitation by microbes in the body
Virus
a pathogen made of a nucleic acid inside a protein shell
Bacteria
a unicellular organism without a true nucleus or organelles
Helminthes
worms
Mycobacteria
A type of bacteria with fungal-type properties
Prions
A small proteinaceous infectious particle.
Routes of infection
Contact Airbourne Droplet Vehicle (common source -- i.e. food, water) Vector (carried by intermediate source)
Pathogenicity
The number of organisms and amount of time required to start a new infectious process
Chain of Transmission
Pathogen or Agent Reservoir Portal of Exit Transmission Modes of entry Susceptible host
What are the lines of defence?
First: mechanical barriers
Second: inflammation
Third: acquired immune response
Defence against infection relies on what two thing?
- Mechanical integrity of epithelial surfaces
2. Decontamination (removal of pathogen)
Three patterns of infections
- Local damage (wart)
- Toxic to host (botulism)
- Widespread effects (HIV)
How does infection spread within a host?
- Directly
- Via natural channels (membranes, vessels)
- Through nerves or phagocytes
Pathogen’s Mode of Action
How the organism produces a pathologic process
What factors affect the occurrence and spread of infection?
- Pathogenic factors
2. Host factors
Pathogen factors affecting occurrence and spread
- Virulence (degree of pathogenicity)
- Dose
- Site of infection
- Synergy between different pathogens
Host factors affecting occurrence and spread of infection.
Resistance to infection
Immune competency
Leukocyte count
Necrosis/Ischemia of tissue
Opportunistic infection
Takes advantage of compromised/defective immune system
Staphylococcal Infections
One of the most common bacteria to reside on the skin
Over 30 subtypes
Leading cause of nosocomial and community acquired infections.
S. aureus
Staphyloccus aureus
Most common staph infection
Nonmotile, anaerobic, hardy. Includes MSRA
Infection can result in: osteomyelitis, respiratory tract infection, infectious arthritis, septicemia, endocarditis, TSS, cellulitis, mastitis
S. pyogenes
Streptococcal pyogenes
One of the most common bacterial pathogens.
Suppurative and non-suppurative
Transmission: contact, droplets, foodborne
Strep throat
Caused by S. pyogenes
Common cause of sore throat.
Pustulant
Scarlet fever
Caused by S. pyogenes
Usually follows untreated strep throat
Impetigo
Caused by S. pyogenes
Skin infection. Usually in children, in hot weather.
Cellulitis
Caused by S. pyogenes
Acute skin infection
S. agalactiae
Streptococcus agalactiae
Normal part of GI flora
Leading cause of neonatal pneumonia, meningitis, sepsis
Infrequent cause of pyrogenic (purulent – pus – but not related to S. pyogenes. sigh) disease in adults
Pregnant women routinely screened.
Necrotizing fasciitis
Caused by S. pyogenes
Serious, potential fatal, spreads quickly along fascial lines.
Pneumococcal infections
Streptococcus pneumonia
Can cause pneumonia, sepsis, otitis media, meningitis
Most common cause of community acquired pneumonia, and of bacterial meningitis
Meningococcal Infections
Can cause meningitis and septicaemia
Anaerobic infections
Not big oxygen fans. Suppurative.
Diptheria
C. diphteria.
Anaerobic
Pseudomembranous pharyngitis
Plague
Y. pestis
Anaerobic
Severe pneumonia, massive lymphadenopathy, high fever –> can progress to septicaemia
Buboes
Enlarges lymph nodes; pathognomic for plague
Botulism
C. botulinum (spore)
Anaerobic
Food borne or wound borne
Interferes with release of ACh at peripheral nerve endings
Spore
Cell produced by bacillus to withstand extreme conditions. Can remain viable for decades
Cholera
V. cholerae
Anaerobic
Diarrhea –> dehydration, oliguria, shock
Spirochete
Slender, spiral, motile bacteria that lives off dead and decaying matter in soil and water.
Ex. Lyme disease, syphylis
Lyme disease
B. burgdorferi
Vector borne disease (deer tick).
Bull’s eye rash (erythemia migrans), nausea, vomiting, neurological and arthritis-type symptoms
Mycobacteria
Small, slow growing aerobic bacteria
Complex lipid-rich envelope
Tuberculosis
Leprosy
Tuberculosis
Mycobacterium tuberculosis
Leading infectious disease cause of death
1/3 world’s preventable deaths
Systemic, inflammatory
Affects lungs and may disseminate to lymph nodes and other organs.
Characterized by granulomas and then casseous necrosis
Virus
Smallest microorganism
Always pathogenic
Can only reproduce in host cells.
Protein cover.
Herpes virus
Family of virus that can cause
Herpes Simplex 1 Herpes Simplex 2 Varicella-zoster virus Epstein-Barr Cytomegalovirus
Herpes Simplex
HSV 1 – typically oral
HSV 2 – genital
Varicella-Zoster Virus
Causes chicken pox and shingles
Can develop into life threatening pneumonia or encephalitis
Herpes Zoster
Shingles
Epstein-Barr Virus
Infectious mononucleosis
Cytomegalovirus
CMV
Symptoms similar to mono
Can cross placenta and cause congenital defects
Enterovirus
Member of picornavirus (small RNA virus)
Includes hand/foot/mouth, poliomyelitis
Post polio syndrome
In 25-50% of people who have had polio, 15-30 years later.
Symptoms like chronic fatigue but progressive
Influenza
Fever, cough, headache. Possibly fatal
Rhinovirus
Common cold
URTA
Acute, afebrile, self-limiting
Mycosis
Any disease caused by fungus
Can be superficial or systemic
Fungal pneumonia
Pneumocystis carinii or jirovecli
Extremely serious form of pneumonia
Yeast infections
Candida albicans
GI tract, mouth (thrush), genitals (candidiasis)
Genital warts
Human papillovirus
Higher incidence of cervical, anorectal and bladder cancers.
Chlamydia
Chlamydia trachomatus
3 million new cases/year
Most common bacterial STI
No symptoms, or pain with intercourse, dysuria, bleeding
Gonorrhea
Neisseria gonorrhoeae
650,000 new cases/year
In men: urethritis, urgency, paining
In women: no symptoms, or slight pain with urination, intercourse
Hepatitis B
Hep B Virus
Can be passed through breastfeeding
77,000 new cases/year
Jaundice, arthralgias, rash, dark urine, anorexia …
Can relapse at the end of treatment.
Cannot be eliminated.
Syphillis
70,000 new cases a year
Treponema pallidum
Unprotected sexual contact, contact with skin and mucous membranes, transplancental, blood transfusions
Primary, secondary and tertiary syphilis
Primary: Chancre at site of infections
3-8 weeks after
Secondary: flu like symptoms and rash 6 weeks to 2 years
Tertiary: severe, CV and CNS up to 20 years later.
Vaccination
Any suspension containing antigenic molecules derived from microorganism given to stimulate an immune response to infectious disease.
Most common cause of bacterial meningitis is non-teens.
Pneumococcus infection.
